根据所给句子，用所给的单词、汉语或首字母的适当形式填空 ，每空一词。

1. Tim has a strange bird,                name is dodo. (it)

2. Christmas is in the ________ month of a year. (12)

3. We are looking forward to ________ you at our party. (see)

4. The food we eat during our lives is the               of six elephants. (weigh)

5. If it is ________ tomorrow, we will go to the park. (sun)

6. They ________(计划) a trip to the Great Wall two days ago.

7. Simon is ________ (着迷的) about football so he often reads a book about football.

8. Our teacher went out without ________(说) a word.

9. The little boy has a good m               . He can remember things very quickly.

10. Neil is a b________ boy. He always helps those persons in danger.

• A．条件(1)充分，但条件(2)不充分．
• B．条件(2)充分，但条件(1)不充分．
• C．条件(1)和(2)单独都不充分，但条件(1)和条件(2)联合起来充分．
• D．条件(1)充分，条件(2)也充分．
• E．条件(1)和(2)单独都不充分，条件(1)和条件(2)联合起来也不充分．

数列{a_n}的前n项和

(1){a_n}是等比数列，a₁=1，q=2；
(2){a_n